I recently purchased a 1.2 8x8 yellow matrix from Adafruit, along with a HT16K33 backpack for it. I joined the matrix and the backpack, connected everything to the arduino, followed the instructions on the site and got it to work. During animation certain rows would not light up and upon later examination I realized that I had to solder up the pins to the backpack because some pins would not completely make contact with the backpack. After soldering the matrix to the backpack, I fired up arduino and uploaded the matrix8x8 sketch that comes with the library to test the matrix and nothing happens.

I don't have a multimeter yet, but tried to check whether electricity is reaching the backpack which turns out to be true. (used a led and connected it to both + and -, and data and clock pins on the backpack.) in both cases the led lights up.

How can I check the health of the backpack and/or matrix?

  • Buy a multimeter. It's the single most essential tool for anyone doing anything with electronics. You cannot exist without one. Go out and buy one immediately. It doesn't have to be an expensive one - as long as it can test voltages and has a diode test (or continuity test 'beep' function) it will suffice.
    – Majenko
    Oct 14, 2015 at 11:19

1 Answer 1


I hate to say it, but a multimeter would really come in handy for you. Harbor Freight has some for under $10.

That said, without knowing anything specific about what you are using, you could try using the same LED you used to test power and put it in parallel with one of the LEDs on the matrix. I'm guessing you don't have power at the LEDs though because it seems unlikely that all the LEDs would fail. Check your solder work and make sure you have not shorted anything. Also, you could have overheated a component when soldering causing it to fail. Good luck.

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